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One of the largest investigations of prenatal hormones in first-time expecting couples found that men had significant prenatal declines in their testosterone and estradiol, but no change in their cortisol or progesterone.

Pregnant women have large prenatal increases in testosterone, cortisol, estradiol, and progesterone, an anticipated result expected in women. However, new studies in men suggest becomming a father might also cause men's hormone levels to change just as women change.

"Other studies had shown that men's hormones change once they become fathers, but our findings suggest that these changes may begin even earlier, during the transition to fatherhood.

"We don't yet know exactly why men's hormones are changing. These changes could be a function of psychological changes men experience as they prepare to become fathers, changes in their romantic relationships, or even physical changes that men experience along with their pregnant partners."

More studies will be needed to find out whether a fathers' prenatal hormone changes are also linked to postpartum or after delivery behavior as well as other parental adjustments as well.

Objectives
Expectant mothers experience marked hormone changes throughout the transition to parenthood. Although similar neuroendocrine pathways are thought to support maternal and paternal behavior, much less is known about prenatal hormone changes in expectant fathers, especially in humans.

Methods
We examined longitudinal changes in salivary testosterone, cortisol, estradiol, and progesterone in 29 first-time expectant couples (N = 58). Couples were assessed up to four times throughout the prenatal period, at approximately weeks 12, 20, 28, and 36 of pregnancy. We also examined within-couple correlations in hormones. Data were analyzed using dyadic growth curve modeling.

Results
As expected, women showed large prenatal increases in all four hormones. Men showed significant prenatal declines in testosterone and estradiol, but there were no detectable changes in men's cortisol or progesterone. Average levels of cortisol and progesterone were significantly positively correlated within couples.